1. Field of the Invention
This invention relates to an apparatus for analyzing a sample with a supercritical fluid. More particularly, it relates to an apparatus of simple construction which employs a supercritical fluid for extracting certain components from a solid sample, and analyzing them.
2. Description of the Prior Art
While an organoleptic test by skilled persons has for a long time been relied upon for the identification and evaluation of the flavor (volatile components) of coffee bean powder, food, cosmetics, perfumes, etc., attention has recently come to be directed to the use of gas chromatography for the analysis and evalution of those volatile components as described, for example, in "Nippon Shokuhin Kogyo Gakkaishi", vol. 30, No. 3, pages 133 to 139 (1983). According to this method, volatile components are collected from a sample by condensation or adsorption, and analyzed and evaluated by an ordinary gas chromatographic technique.
This gas chromatographic method, however, still has a lot of problems, since it employs a solid sample having a very low concentration of volatile components and has to wait for the volatilization of the volatile components for their collection. It requires a sample quantity which is as large as at least 10 g. It has a low degree of detection sensitivity. It requires a lot of time for collecting the volatile components. It involves a complicated procedure for the condensation or adsorption of the volatile components.
A supercritical fluid obtained by compressing and liquefying carbon dioxide or other substance which is a gas at ambient temperature and atmospheric pressure is characterized by its excellent ability to dissolve various kinds of substances. This characteristic is utilized in a known technique for extracting components from various substances as described, for example, in Anal. Chem., vol. 54, No. 4, pages 736 to 740, April 1982 and International Laboratory, pages 12 to 23, June 1984.
As a supercritical fluid is very liable to gasification, however, a lot of care is required for its transportation so that it may not gasify. For example, it is necessary to use a pump having a high compression ratio. An extremely large and complicated apparatus is, therefore, required for the analytical operation which employs a supercritical fluid, and is has hitherto been considered that a supercritical fluid is difficult to employ for analytical purpose.